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June 28, 2012

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Quick Introduction to GIMP

by noise

Today’s article will be a quick introduction to the GIMP, a free and open source
image editing program, which can be successfully be used for creating and editing textures
or concept art.

You can get the program at the following link (currently at the 2.6.11 stable version):
http://www.gimp.org/downloads/

After you’ve installed and run it, three floating main windows will appear:

You can maximize the middle one (which will contain the digital canvas) and put the
other two on the sides, for a better ergonomy.

If you’re familiar with any image editing software (e.g. Photoshop, PaintShop, etc)
you will already recognize, in the Toolbox, some useful tools. If you’re not familiar,
don’t worry, I will get through some of the most important ones.

Navigation

Let’s first create a new blank image, to have something to work on it. Go to File > New,
leave the default values and press OK.

To zoom in and out the preview of the image/canvas, hold down CTRL then
Scroll the Mouse’s Wheel.

To pan the image, press MMB and drag.

To undo or redo, there are the classic usual keys combination CTRL+Z and CTRL+Y

Layers

To work more efficiently and be more flexible, we will use the GIMP’s layer system, similar
with other image editing software. To access the layers docked window, press the layers icon.

Here, we’ll observe that we already have a white background layer which was created by default
when we first created the image.

When you will draw or select something from an image, you will affect only the current selected
layer.

We can change the opacity of the current selected layer by adjusting the Opacity slider, and also
change the blending mode from the option above. Blending modes are useful to determine how two or
more layers are blended into each other.

For example let’s create two white layers by pressing this button on the bottom of the layers’ window.
Choose white then press OK.

TIP: you can also duplicate a layer and delete it with the buttons described in the previous
image

Select the bottom layer and choose the Paintbrush tool (from the left side panel).

Choose a dark color from the color swatches – I choose black – and draw something random.

You will observe that nothing happens, but if you will take a closer look, at the layer’s icon,
the drawing is there but obscured by the above layer which is opaque white.

You can adjust this in more ways. One will be just to hide the above layer by selecting the eye
icon near the layer’s name.

Or, adjust the opacity of the top layer.

Or simply choose the Multiply blending mode (feel free to experiment with the others blending modes,
keeping in mind that for some of them you’ll need to have some colors/gray values on that layer).

Drawing

Now let’s talk a bit about the paint/drawing tools. Probably the tool that you will use most will be
the Paintbrush tool (P hotkey). This is pretty straight forward, you paint with a
predefined brush, with a chosen color.

You can adjust blending modes, opacity, brush types,the size, dynamics (useful with graphic tablets),
etc. from the settings menu located under the Toolbox.

TIP: to quickly adjust the brush size, simply press [ and ] keys.

You also have an eraser tool to delete the current pixels from a selected layer.

To use a gradient tool , simply left mouse click then drag to set the direction and
the size of the gradient.

You also can choose from a list of gradient presets from the right dock window, by clicking on the
gradient icon.

Use fill tool , to fill with a chosen color (or pattern) a certain layer or
selection.

Text tool - you can add text to your image using this tool

The layers can be easily rotated, moved, scaled or free transformed using the corresponding
buttons.

Move tool - click and drag to move the layer.

Rotate tool - you can either click and drag or adjust the parameters from
the new opened window.

Scale tool - you can either click and drag or adjust the parameters from the
new opened window.

Perspective tool - you can distort the image by click and drag one of its
corners.

Flip tool - click to flip the image (choose Horizontally or Vertically from
the left side panel options).

Selection

There are also some very useful selection tools, like rectangle ,
ellipse and free select tool .

The free select tool is also known in other programs like the lasso tool. If you click, hold and
drag, you will make a selection exactly after the cursor’s movement.

If you release it, then point and click, you will make a straight selection line between the
clicked points (similar to polygonal lasso tool from Photoshop).

Adjustments and Filters

You can easily adjust the colors or values for a selected layer in Colors > choose the
desired adjustment.

TIP:It’s best to make a duplicate of the layer that you’ll want to modify, in case you’ll
change your mind later or you just want to use the same original image with another effect.

The effects and filters can be found in Filters > choose the filter from the list, then adjust
its parameters from the pop-up window, where is the case.

Being just an introduction to this program, please feel free to experiment with these effects and
filters (and the other stuff you learn today), and until next time, have fun !

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